The present invention relates to a constant velocity universal ball joint. The joint has an outer joint part and an inner joint part each provided with a plurality of ball tracks which extend substantially in the longitudinal direction. Balls are provided for torque transmitting purposes and are guided in the radially opposed tracks in the outer joint part and in the inner joint part. A cage is included which, in cage windows, holds each ball in a plane positioned perpendicularly relative to the axis. The cage includes a means to guide the cage with the balls on to the angle-bisecting plane, if the axes of the outer joint part and the inner joint part deviate from one another. The invention is utilized with different types of joints which will be described below.
In particular, the invention refers to Rzeppa fixed joints where direct control of the balls onto the angle-bisecting plane is effected by meridionally extending ball tracks. In this case the centers of the tracks of the inner joint part and outer joint part are offset in the longitudinal direction. Further, the invention refers to undercut-free UF joints which, basically follow the same principle as Rzeppa joints, but, if viewed axially, the ball tracks are designed to be undercut-free. Additionally, there are double offset DO joints where the inner face and outer face of the cage are provided with spherical guiding faces. The guiding faces have curvature centers which are axially offset relative to one another. Thus, when the joint is articulated, the cage is controlled directly and the balls indirectly so as to move onto the angle-bisecting plane. These joints may be produced with curved ball guiding tracks in the form of fixed joints and with straight ball guiding tracks in the form of axially plungeable joints.
Finally, VL joints are covered by the subject of the invention. VL joints, in their outer and inner joint parts, include tracks which are associated with one another and which at least part of do not extend strictly in the longitudinal direction but forman angle relative to one another. As a result of this orientation, the balls are directly controlled to the crossing of said tracks and move on to the angle-bisecting plane and onto half the plunging path.
With prior art joints of these types, the cages are either permanently or at least temporarily in sliding contact with the entire surfaces of the inner and/or outer joint part positioned between the ball tracks. Depending on the design of the surfaces, the contact permanently affects spherical portion faces or only wandering narrow annular portion faces. For wear reasons, it is essential that all sliding faces be hardened at the outer joint part and/or inner joint part. The hardening operation leads to the introduction of a great deal of heat which leads to hardness distortion and deformation of the parts. As a result, the distorted guiding faces of the parts must be machined after hardening. Or, if the parts are produced to their finish dimensions prior to hardening in order to eliminate the subsequent grinding operation, the hardness distortion at least requires classification to ensure the outer joint parts, inner joint parts and cages are selected to match one another. Both the grinding operation after hardening and classification after hardening increase production costs.